bs5-navwalker.css

 /**
 * NAVWALKER BOOTSTRAP 5 
 * Extra levels
 */

.navbar.navbar-expand-lg .dropdown .dropdown-menu .dropdown-submenu {
    /* dropdown sub menu positioning */
    margin: 0;
    left: 100%;
}

.dropdown-menu {
    padding: 0;
    border-radius: 4px;
    box-shadow: 0 1px 3px 0 rgb(0 0 0 / 10%);
}

.dropdown .dropdown-submenu {
    top: 0;
    left: 100%;
    margin-left: 0.125rem;
}

.navbar .dropdown-item {
    padding: 0.5rem 1.8rem;
}

.dropdown-item:hover,
.dropdown-item:focus {
    /* Item that could be selected now */
    background: #7aacde !important;
    color: white !important;
}

.dropdown-item.active,
.dropdown-item:active {
    /* Selected item (ie page now active) */
    background-color: transparent;
    color: #212529;
    font-weight: 600;
}

.nav-item a {
    /* ensure No flashing in links */
    transition: none !important;
}

.navbar-nav li:hover>ul.dropdown-menu {
    /* controversial will open on hover */
    /* display: block; */
    font: inherit;
}

@media (min-width: 992px) {
    /* ONLY DESKTOP - Convert toggle to right > in deeper levels */
    .at_depth_1 .dropdown-toggle::after,
    .at_depth_2 .dropdown-toggle::after,
    .at_depth_3 .dropdown-toggle::after {
        display: inline-block;
        margin-left: 1.5em;
        vertical-align: 0.255em;
        content: "";
        border-top: 0.3em solid;
        border-right: 0.3em solid transparent;
        border-bottom: 0;
        border-left: 0.3em solid transparent;
        left: 0;
        /* rotate right */
        -ms-transform: rotate(-90deg);
        /* IE 9 */
        -webkit-transform: rotate(-90deg);
        /* Chrome, Safari, Opera */
        transform: rotate(-90deg);
    }
}

@media (max-width: 991.98px) {
    /* Smaller devices remove shadow & border from children */
    .offcanvas .dropdown-menu {
        border: none;
        box-shadow: none;
    }
    /* Smaller devices offcanvas, add indent */
    .depth_1 .dropdown-item {
        margin-left: 10px;
    }
    .depth_2 .dropdown-item {
        margin-left: 15px;
    }
    .depth_3 .dropdown-item {
        margin-left: 20px;
    }
}